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I'm just talking about the balanced rig concept. You need to have enough ditchable weight so that you can swim your rig up if you lose all buoyancy. There is also an amount of weight that's safe to ditch at the beginning of the dive where buoyancy problems are most likely to surface - you can use that number to assist in calculating how much ditchable weight you want to use.
(This is usually irrelevant unless you are diving very deep with a highly compressible wetsuit)
So, if you had a hole in at the surface, you'd drop weights, but if you had a big gaping hole at depth that prevented the BC from holding any air, and you'd keep your weights? Am I understanding this correctly?
If the "balanced rig" is the answer here - then why isn't it an answer at the surface?
She is a drysuit diver...so has two sources of buoyancy
If I had a hole in my BP/W...and was at the bottom at say 100 ft, with a 7mm suit on, would I ditch all my weight? No. Might I have to get rid of some of it? yea, but only enough to get off the bottom....although my first choice would be to use my smb to get me off the bottom, and let go of it once I got up enough...ditching all my weight would be a very unhealthy thing to do.
So, if you had a hole in at the surface, you'd drop weights, but if you had a big gaping hole at depth that prevented the BC from holding any air, and you'd keep your weights? Am I understanding this correctly?
If the "balanced rig" is the answer here - then why isn't it an answer at the surface?
The concept at depth is to be neutral, the concept in an emergency is to be positive, thus dropping the weights at the surface (ON THE SURFACE) in an emergency has been taught since the beginning of scuba.
If I had a hole in my BP/W...and was at the bottom at say 100 ft, with a 7mm suit on, would I ditch all my weight? No. Might I have to get rid of some of it? yea, but only enough to get off the bottom.
Ah, big distinction. The question didn't say anything about ditching ALL of your weight - merely "ditching weight".
OK. I see that a couple of you really understand the concept of buoyancy. My own opinion is pretty much that of TSnM's. Drop weight on the surface, maybe. As far as dropping weight/weights on the bottom would mean that you are overweighted in the first place if you can't swim up. I'd keep as much weight on as I could so as not to accelerate to the surface. If there is a down line, who cares. Just hold on and do your stops.
Last edited by Garrobo; January 7th, 2009 at 11:08 AM..
Reason: spelling
This is one of the reasons that very deep diving in thick neoprene is strongly discouraged by the people who trained me. You can lose over 20 lbs of lift when 14 mm of neoprene (common as a core layer for wetsuit divers here) is compressed at 100 fsw. It would be difficult to swim up a rig that was 20 lbs negative (but of course, that requires that you have lost ALL ability of the wing to hold gas). So you ditch weight. And, of course, as you ascend, you get that lift back, and lose control of your ability to stay underwater. It's an ugly sequence. Better bent than drowned, but I'd rather dive a rig where I'm not faced with the choice. Diving deep and cold? Dive dry, or carry some significant auxiliary lift.
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This is one of the reasons that very deep diving in thick neoprene is strongly discouraged by the people who trained me. You can lose over 20 lbs of lift when 14 mm of neoprene (common as a core layer for wetsuit divers here) is compressed at 100 fsw. It would be difficult to swim up a rig that was 20 lbs negative (but of course, that requires that you have lost ALL ability of the wing to hold gas). So you ditch weight. And, of course, as you ascend, you get that lift back, and lose control of your ability to stay underwater. It's an ugly sequence. Better bent than drowned, but I'd rather dive a rig where I'm not faced with the choice. Diving deep and cold? Dive dry, or carry some significant auxiliary lift.
Absolutely. I dive such a wetsuit, and when I go deep I have a 50# lift bag that could double as a wing if needed. What I was thinking in my above post was if I had no gas left as I cut through the last of lines trapping me, I have no ability to use any lift, wing, bag, or suit.
On the + side, I don't do deep, cold, entanglement hazardous dives solo, so probably this is all academic...
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